<template>
  <div class="pagination">
    <!--@click="$emit('getPageNo',pageNo-1)"自定义事件跳转上一页-->
    <button :disabled="pageNo==1" @click="$emit('getPageNo',pageNo-1)">上一页</button>
    <button v-if="startNumAndEndNum.start > 1" @click="$emit('getPageNo',1)" :class="{active:pageNo==1}">1</button>
    <button v-if="startNumAndEndNum.start > 2">...</button>

    <!-- 生成从 start 到 end 的数字序列 -->
    <button v-for="page in generateRange(startNumAndEndNum.start, startNumAndEndNum.end)" :key="page" v-if="page >= startNumAndEndNum.start && page <= startNumAndEndNum.end" @click="$emit('getPageNo',page)" :class="{active:pageNo==page}">{{ page }}</button>

    <button v-if="startNumAndEndNum.end < totalPage - 1">...</button>
    <!--:class设置点击之后变成蓝色-->
    <button v-if="startNumAndEndNum.end < totalPage" :class="{active:pageNo==totalPage}">{{ totalPage }} </button>
    <button :disabled="pageNo==totalPage" @click="$emit('getPageNo',pageNo+1)">下一页</button>
    <button style="margin-left: 30px">共 {{ total }} 条</button>
  </div>
</template>

<script>
export default {
  name: "Pagnation",
  props: ["pageNo", "pageSize", "total", "continues"],
  computed: {
    totalPage() {
      return Math.ceil(this.total / this.pageSize);
    },
    // 计算出连续页码，起始数字以及结束数字
    startNumAndEndNum() {
      let start = 0,
        end = 0;
      if (this.continues > this.totalPage) {
        start = 1;
        end = this.totalPage;
      } else {
        start = this.pageNo - parseInt(this.continues / 2);
        end = this.pageNo + parseInt(this.continues / 2);

        if (start < 1) {
          start = 1;
          end = this.continues;
        }
        if (end > this.totalPage) {
          end = this.totalPage;
          start = this.totalPage - this.continues + 1;
        }
      }
      return { start, end };
    },
  },
  methods: {
    // 生成从 start 到 end 的数字序列
    generateRange(start, end) {
      const range = [];
      for (let i = start; i <= end; i++) {
        range.push(i);
      }
      return range;
    },
  },
};
</script>


<style lang="less" scoped>
.pagination {
  text-align: center;
  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #409eff;
      color: #fff;
    }
  }
}
.active{
  background: #409eff;
}
</style>